I have installed Ubuntu server edition on a computer. During the installation I skipped the network configuration, and now I don't know how to connect to the internet via LAN / Ethernet.
First, verify that you have a valid ethernet interface; ideally eth0:
See if you can connect temporarily:
sudo dhclient eth0
If you connect, edit /etc/network/interfaces to set a static IP address appropriate for a server:
sudo vim /etc/network/interfaces
I suggest the following, adjusted, of course to suit your network:
auto lo iface lo inet loopback auto eth0 iface eth0 inet static address 192.168.1.150 netmask 255.255.255.0 gateway 192.168.1.1 dns-nameservers 18.104.22.168 192.168.1.1
Save the file and quit vim. Be sure to use an IP address outside the range of the DHCP pool in the router so as to avoid collisions. Get the system to read and use the changes:
sudo ifdown eth0 && sudo ifup -v eth0
ping -c3 www.google.com
If you get ping returns, you are all set.